Cardiopulmonary exercise capacity and limitations 3 months after COVID-19 hospitalisation

Background This study aimed to describe cardiopulmonary function during exercise 3 months after hospital discharge for COVID-19 and compare groups according to dyspnoea and intensive care unit (ICU) stay. Methods Participants with COVID-19 discharged from five large Norwegian hospitals were consecutively invited to a multicentre, prospective cohort study. In total, 156 participants (mean age 56.2 years, 60 females) were examined with a cardiopulmonary exercise test (CPET) 3 months after discharge and compared with a reference population. Dyspnoea was assessed using the modified Medical Research Council (mMRC) dyspnoea scale. Results Peak oxygen uptake (V'(O2peak)) <80% predicted was observed in 31% (n=49). Ventilatory efficiency was reduced in 15% (n=24), while breathing reserve <15% was observed in 16% (n=25). Oxygen pulse <80% predicted was found in 18% (n=28). Dyspnoea (mMRC >= 1) was reported by 47% (n=59). These participants had similar V'(O2peak) (p=0.10) but lower mean +/- sD V'(O2peak).kg(-1) % predicted compared with participants without dyspnoea (mMRC 0) (76 +/- 16% versus 89 +/- 18%; p=0.009) due to higher body mass index (p=0.03). For ICU- versus non-ICU-treated participants, mean +/- sD V'(O2peak) % predicted was 82 +/- 15% and 90 +/- 17% (p=0.004), respectively. Ventilation, breathing reserve and ventilatory efficiency were similar between the ICU and non-ICU groups. Conclusions One-third of participants experienced V'(O2peak) <80% predicted 3 months after hospital discharge for COVID-19. Dyspnoeic participants were characterised by lower exercise capacity due to obesity and lower ventilatory efficiency. Ventilation and ventilatory efficiency were similar between ICU-and non-ICU-treated participants.